Collapsible cores have been manufactured for many years, as shown in U.S. Pat. No. 3,247,548. This patent discloses a collapsible core for molding threaded container caps. According to this patent, a one-piece core is longitudinally divided into a plurality of circumferentially disposed sections. The sections include inner and outer ribs that are formed into a common base. The sections are resilient in a radial direction and when radially unsupported are in a collapsed position. When a pin is inserted into a central channel of the sections, the sections are held in an expanded condition, used for molding. When molding is completed, the pin is withdrawn, and the sections collapse so that the cap can be removed.
The present inventor has recognized that the core as described in the aforementioned patent suffers the drawback that the core is expensive and difficult to manufacture. The present inventor has recognized that it would be desirable to provide collapsible core that was more cost effectively manufactured and more effectively operated.